Fish are survivors. And when the water starts getting cold, they head for deeper waters, where the chilling effects of winter air are less pronounced. Provided there’s adequate aeration, your fish will likely linger at the bottom throughout the colder months. As a result, they’ll be much less visible – but the odds are extremely good they’re doing just fine.

In order to ensure there’s sufficient oxygen for the winter, some people opt to keep their aeration systems active all year ‘round. At the very least, though, it’s important to maintain a vent hole when – or if – your pond ices over. The vent hole allows harmful decomposition gases to escape, allowing fish to winter safely. And because their metabolism slows during the winter months, a properly vented pond will likely have sufficient oxygen to ensure the survival of your fish until springtime.

Fish, it turns out, are extremely resilient. After wintering in the lower reaches of your pond, your fish will gradually return to the upper levels once water temperatures start to rise. In general, it’s probably a good sign when fish become less visible. If they’re struggling, it’s far more likely you’d see them at the edges of your pond. So while you might miss them, your invisible fish are probably doing just fine.

2 Responses

We have an areation system in our pond that utilizes 3 difusers. Our acre sized pond is set up like a swimming pool where one end is shallow (3′-4′ deep), the other end is deep 10′ – 12′ deep), with a slope between both ends. My husbnd and I are wondering which difuser we should keep on during the winter. I think we should turn the one off in the deep end so the fish have a area of warmer water to spend their time in. Or am I wrong and should that difuser be the one we keep on? I want our fish to have the best chance at wintering over. We are in the Green Bay, WI area and our winters get pretty cold. It is not unusual to have temps well below Zero for weeks on end. We’ve been lucky so far this season and it has been hovering around 32 degrees for the last couple of weeks.

That is a great question Sue. You win the debate on this one. while super-cooling is uncommon, placing your aeration plates at the absolute bottom of you pond in extreme hot or cold temperatures eliminates any possibility for your fish to escape to friendlier water as you are circulating the entire pond. In extreme weather it is ideal to drag your plates to shallower areas (or in your case cut airflow to your deepest plate) to provide a small thermocline for your fish to retreat to if need be. Running your shallower plate will still keep a hole open in surface forming ice for proper air-exchange and, while you are not aerating the entire pond, there should still be plenty of oxygen being added to get them through to spring when you can turn both plates on again.